UK aid agencies raised £71m in their Pakistan floods appeal last year, the third highest amount raised for a humanitarian disaster, according to the Disasters Emergency Committee (DEC), the umbrella organisation of British humanitarian groups.

The DEC itself raised £41m and member agencies raised £30m, an appeal only surpassed by amounts raised for the 2004 tsunami and 2010 Haiti earthquake.

Monsoon rains that began in late July 2010 were the most severe in Pakistan's history. The flash flooding in the mountains of the north-west eventually spread to the south, through the Indus and other river systems, to engulf an area the size of the UK. Aid provided emergency shelter for 290,000 people, clean water for 510,000, and safe toilets for 160,000.

The report found that DEC agencies initially struggled to meet the most urgent needs of the worst affected survivors as they began returning in vast numbers from temporary camps to their ruined villages within weeks of being displaced.

"All disasters are a tragedy for those caught up in them, but the Pakistan floods were exceptional because of the vast number of people affected," said the DEC chief executive, Brendan Gormley. "The response to our appeal was extremely generous and the UK public can be proud that the massive aid effort they helped fund has already provided support to 1.8 million people."

Duplication, a familiar bugbear of relief operations, remained a problem, the report said.

"While there have been few cases of joint assessments, overall co-ordination has improved with time, leading to concrete benefits in identifying priority areas, avoiding duplication and developing joint technical standards," it said. "However, some duplication is still present and the wider benefits of co-ordination, such as joint assessments/programming, fundraising and advocacy, are still not evident."

The report urged agencies to carefully pick local NGO partners, given the negative image of local NGOs in some areas and to engage with "women more strategically and use them as agents of positive change". One way of doing this, the report said, is to hire more women in aid teams and to set up separate committees for women and girls.

Agencies were also urged to assemble and pass on information that would help deal with future emergencies.

"Lessons learned are only embedded within staff in most cases, and formal processes and documents to capture previous learning, and to document and disseminate current learning, are generally missing," the report said.

The evaluation of the response to last year's floods comes amid a UN warning of people at risk from floods expected in the coming months. The UN said last week that up to 5 million people in Pakistan are at risk, partly due to poor reconstruction and the inadequate rehabilitation of survivors from last year's disaster. However, as Pakistan braces itself for its annual monsoon season – which runs from late June to early September – the UN says authorities and aid organisations have learned lessons and are better prepared, even for the worst case scenario.

The UN last year appealed to the world for almost $2bn – the biggest appeal launched by the body for any humanitarian emergency. Yet 30% of the appeal remains unfunded almost one year on.